Field of the Invention
The present invention relates to alpha-amylase variants, polynucleotides encoding the variants, methods of producing the variants, and methods of using the variants.
Description of the Related Art
Alpha-amylases (alpha-1,4-glucan-4-glucanohydrolases, E.C. 3.2.1.1) constitute a group of enzymes, which catalyses hydrolysis of starch and other linear and branched 1,4-gluosidic oligo- and polysaccharides.
Alpha-amylase is a key enzyme for use in detergent compositions and its use has become increasingly important for removal of starchy stains during laundry washing or dishwashing.
Some detergents, in particular dishwashing detergents, contain bleaching systems, bleach activators, and bleach catalysts which are all very destabilizing for the alpha-amylases due to oxidation of the molecules. Therefore, it is important to find alpha-amylase variants, which are stable, have high wash performance, stain removal effect and/or activity in detergents comprising various bleaching agents.
It is known in the art to stabilize alpha-amylases towards bleaching agents and oxidation by these by substituting the methionine at position 197 (using the amylase from B. licheniformis for numbering) with e.g. leucine. This has e.g. been disclosed in WO199418314. However, these prior art oxidation stable alpha-amylases have the disadvantage that the alpha-amylase activity is reduced.
Thus, it is an object of the present invention to provide alpha-amylase variants that exhibit a high level of stability in detergents, in particular in dishwashing detergents and other detergents comprising bleaching agents or systems but at the same time have improved alpha-amylase activity compared to the parent alpha-amylase having the prior art solution of M197L substitution. It is a further object to provide alpha-amylase variants which have high performance, in particular high wash performance, in particular high dishwashing performance.
The present invention provides alpha-amylase variants with improved stability compared to its parent and improved activity compared to its parent having M197L (which in the parent amylases of the present invention corresponds to M202L).